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In March, I reported on the 2013 Census of Missouri Public Water Systems. It is basically a count of the number of water systems in the state, their type, the kind of source from which they intake their water, and the kind of treatments they give the water. (See 2,738 Public Water Systems in Missouri.)

The Department of Natural Resources also publishes an annual report on the quality of public drinking water. The 2012 Annual Compliance Report of Missouri Public Drinking Water has now been published. The results improve slightly on the trends seen in 2011.

The trends are shown in the graphs at right. The dips in 2007 and 2010 resulted from water treatment errors at Missouri American Water Co., the water provider for portions of the St. Louis Metropolitan Area. The problems were of very short duration, and no illnesses were reported as a result.

The largest number of violations were violations of the Total Coliform Rule. There are many species of coliform bacteria, and they occur naturally in the soil. Mostly they are not harmful to human health. However, they are also plentiful in the digestive tracts of animals, so the presence of too many coliform bacteria in water, or the presence of a specific kind of coliform bacteria, E. Coli, can be used as markers that contamination may have occurred. The contamination may include bacteria that are harmful to human health. Thus, water systems with a Total Coliform Rule violation receive extra scrutiny to determine the source. An Acute Coliform Violation, or the presence of E. Coli, results in a boil order.

Because water is tested in so many different ways, and the tests are repeated monthly, large numbers of violations are theoretically possible each year. The DNR is typically most concerned with water systems that have repeated violations, or water systems that have a violation of monitoring requirements and a history of bacteriological contamination.

Thirty systems had repeated major monitoring violations (down from 34 in the 2011 report). Ten were in Camden County, 4 in Jefferson County, and 4 in Stone County. Thirty-one systems had three or more major total coliform violations, plus a history of monitoring violations ( down from 45 in the 2011 report). Of these, four were in Green County, four were in Newton County, and three were in Stone County.